The invention relates to a method for installing tensioned strip-shaped tension members on supporting structures, particularly concrete supporting structures, wherein the tension member is tensioned at least at one end by means of a tensioning device clamped via a temporary clamping anchor fastened to the tension member, and is then anchored to the supporting structure by means of a permanent anchoring device.
To increase the load-carrying capacity (strengthening) or for recovery of the original load-bearing capacity (rehabilitation) of supporting structures, particularly supporting structures of steel and reinforced concrete, it is known to subsequently install strip-shaped tension members on the surface of the supporting structure, preferably plate-like tension members of plastic with fibers, particularly carbon fibers, embedded for reinforcing. If these tension members are anchored in the pre-stressed state, the load-bearing capacity and the use capability are additionally considerably improved. It is known (DE 198 49 605 A1) to anchor for this purpose the strip-shaped tension members arranged flush with the surface on steel baseplates which are let into the concrete surface.
Supporting structures of steel or wooden components can be rehabilitated or strengthened in a corresponding manner.
The production of the recess, necessary for this purpose, in the concrete surface in the region of the anchoring devices is expensive and can lead to damage to the reinforcement embedded in the concrete. What makes matters worse is that this necessary recess at the clamping end of the tension member depends not only on the size of the baseplate provided for permanent anchoring, but also on the clamping path of the clamping device arranged there. These recesses are therefore of considerable size in the case of long tension members which require a large clamping path. The baseplate remaining in the concrete supporting structure also increases the costs of anchoring the tension member.
The invention therefore has as its object to provide a method, of the category named at the beginning, such that the anchoring of tension members flush with the surface is substantially simplified.
This object is attained according to the invention in that the tension member is tensioned by means of the temporary clamping anchor at a distance from the surface of the supporting structure, and that the tension member is then pressed onto the surface by means of at least one permanent anchoring clamp.
Since the tension member is located during the tensioning process at a distance from the surface of the supporting structure, the ends of the tension member can be fastened by clamping to temporary clamping anchors on a clamping plate of the temporary clamping anchor, located under the tension member, without a recess having to be produced for this clamping plate in the surface of the supporting structure. By means of the subsequent pressing of the tension member onto the surface by means of a permanent anchoring clamp, the frictional connection is produced between the tension member and the supporting structure, the strip-shaped tension member now being arranged flush to the surface. The introduction of the tensioning force takes place using the pressing force of the anchoring clamp, so that the temporary clamping anchor arranged between the anchoring clamp and the end of the tension member can be removed.
It is thus no longer necessary to provide a baseplate remaining on the supporting structure and to produce a recess for sinking this baseplate. New fields of application in which recesses for the baseplate and the clamping path are not actually possible are thus opened up for the method, so that even carrying the method over to steel supporting structures or wooden supporting structures is made possible.
A further particular advantage of the method according to the invention consists in that it can also be used with arched supporting structures, particularly concrete supporting structures, for example floor slabs in bridge building, wherein the tensioning force of the tension elements can be introduced directly at the edge of the arch. This is not possible with the conventional way of installing clamped strip-shaped tension members on concrete supporting structures. The tensioning force cannot be directly introduced to the arch, at least on the clamping anchor side, since the recess required for the clamping device would penetrate too far into the arch region and possibly the arch reinforcement would be penetrated.
As a development of the invention, it is provided that the tension member is clamped between two temporary clamping anchors fastened at the two ends of the tension member, at a distance from the surface of the supporting structure, and that the tension member is subsequently pressed onto the surface near its two ends, each by means of a respective permanent anchor clamp.
The invention also relates to an apparatus for carrying out the method. Starting from a known apparatus (DE 198 49 605 A1) with a strip-shaped tension member, which is connected at least at one end to a temporary clamping anchor, with a tensioning device engaging on the temporary clamping anchor during the tensioning process, and with a permanent anchoring device, the apparatus according to the invention is characterized in that a baseplate of the temporary clamping anchor is arranged between the tension member and the surface of the supporting structure, and in that at least one permanent anchoring clamp engages over the tension member near the temporary clamping anchor and can be pressed against the surface.
In comparison with the known apparatus, the apparatus according to the invention is substantially more cost-effective, since no permanent clamping plates remain on the supporting structure, and since no recesses have to be provided for these in the surface.
The strip-shaped tension member can be pressed directly onto the surface. In embodying the concept of the invention, it is also possible to arrange between the tension member and the surface of the supporting structure and/or the anchoring clamp, an adhesive layer which hardens after the tension member has been pressed onto the surface.
The adhesive layer enhances or takes over the force-transmitting connection between the tension member and the surface or the anchor clamp respectively.
It is also possible to adhere an intermediate layer which increases friction and/or distributes load in the region of the anchoring clamp.